(19)
(11) EP 2 249 623 A8

(12) CORRECTED EUROPEAN PATENT APPLICATION
Note: Bibliography reflects the latest situation

(15) Correction information:
Corrected version no 1 (W1 A1)

(48) Corrigendum issued on:
09.02.2011 Bulletin 2011/06

(43) Date of publication:
10.11.2010 Bulletin 2010/45

(21) Application number: 10161528.4

(22) Date of filing: 29.04.2010
(51) International Patent Classification (IPC): 
H05B 33/08(2006.01)
(84) Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TR
Designated Extension States:
AL BA ME RS

(30) Priority: 04.05.2009 IT TO20090357

(71) Applicants:
  • OSRAM Gesellschaft mit beschränkter Haftung
    81536 München (DE)
  • OSRAM S.P.A. - SOCIETA' RIUNITE OSRAM EDISON CLERICI
    20144 Milano (IT)

    IT 

(72) Inventors:
  • Menegazzi, Michele
    31038 Paese (Treviso) (IT)
  • Toscan, Matteo
    31010 Maser (Treviso) (IT)

(74) Representative: Bosotti, Luciano 
Buzzi, Notaro & Antonielli d'Oulx Via Maria Vittoria, 18
10123 Torino
10123 Torino (IT)

   


(54) A low-dropout (LDO) current regulator


(57) A driver device to produce a regulated current (ILED) from an input voltage (VDC1) includes a driver transistor (MOS1) for providing said regulated current (ILED) and a stabilization circuit (T1, D1, R1, R2, R3, RS) acting on the control electrode (P) of the driver transistor (MOS1) to determine a stabilized reference value (ILED) for the regulated current. The stabilization circuit includes a bipolar transistor (T1) coupled (R2, R3) to the control electrode (P) of the driver transistor (MOS1) in a feedback relationship, whereby, with the bipolar transistor (T1) conducting, increase and decrease of said regulated current (ILED) induce decrease and increase of the collector current in the bipolar transistor (T1), respectively. A diode (D1) and a resistance (RS) traversed by the regulated current (ILED) are interposed between the base (B1) and the emitter of said bipolar transistor (T1) in a cascade arrangement, so that the stabilized reference value (ILED) for the regulated current is determined by the value of resistance (RS) as a function of the difference between the base-emitter voltage of the bipolar transistor (T1) and the voltage across the anode and cathode of said diode (D1) .